🚀 go-pugleaf

In article <1992Aug26.021824.930@decuac.dec.com> mjr@hussar.dco.dec.com (Marcus J. Ranum) writes:
>cme@ellisun.sw.stratus.com (Carl Ellison) writes:
>
>>If I give you an RSA key, that's all you need.  I'm the only one in the world
>>who knows the two primes in N.  That defines *me*.
>
>	With the usual caveat that he has to meet you or something so you
>can give him the RSA key. Otherwise I can give him *my* RSA key and ask
>you nicely for yours and just unwrap and rewrap everything that goes past.


That doesn't work.  You could just as easily meet him personally, present
an ID card saying you're me and hand him your RSA key.  To combat the
impersonation attack, we need to make sure that we have the equivalent of a
true broadcast which both the intended recipient and the sender can read.



That's a different point, though.  What I'm trying to point out is that you
deal with me in a very real sense but you've never met me and aren't likely
to.  Therefore, we don't need physical contact in order to communicate.  In
fact, I don't need a flesh and blood body at all.  I could be a computer
which is demonstrating that it has passed the Turing test.  You don't know
and I submit that you don't care.  You'll have the same conversation with
me in any case.


Something like a personal meeting during which keys are exchanged does only
one thing:  establish a relationship between keys and some physical appearance.
If my physical appearahce doesn't mean anything to you, then that relationship
has added nothing to the authentication process.  Therefore, there's no
need to establish it.


So:  what relationships are important to establish?

Eg., if I change keys (aka change names), I can establish the relationship
by announcing the change in a public message which lists both keys and is
signed in both.

If Alice is talking to Bob and Cathy is also talking to Bob, Alice and
Cathy should be able to establish that they're both talking to the same
person by sharing signed messages to/from him with each other.


More practically, it's important to establish a relationship between *me*
and some money in a bank.  If the money is deposited electronically (as
my paycheck has been for over 10 years), it can be deposited to *me* --
ie., to my RSA key.  There doesn't need to be a name or address or any
of that nonsense on my bank account -- just my RSA key.


If I can move money around with only my key and get caught in a love
triangle with only my key, what more do I have to do?  :-)